The present invention relates to container-closure assemblies. More particularly, the invention relates to a so-called "child resistant" container-closure assembly for substances which may be harmful to children and which is designed to prevent opening by a child and yet is manipulatable by adults to remove the closure for access to the container contents. These assemblies are typically used for medicines such as aspirin which in themselves are not harmful but which can present a serious risk to a child if ingested in even moderate quantities.
Child resistant container-closure assemblies are not new per se. Existing assemblies of this type generally comprise a cap made of a resilient plastic material having locking means in the form of lugs, which engage under a rib on the container in one position to secure the cap against removal. The cap, however, is rotatable relative to the container neck to position the lugs in registry with one or more complementary gaps in the container rib and thereby permit removal. The cap and container usually are provided with visible indicia which when aligned present a visual means to the user that the lugs are in registry with the gaps and the cap can be removed. This type of assembly is shown in the U.S. patent to Horvath, No. 3,669,295, issued June 13, 1972. In Horvath the lugs depend from the top of the cap and are spaced radially inwardly from the skirt to engage an internal rib in the container neck and the skirt is provided with a bead at its lower edge which snaps over a bead on the exterior wall of the neck of the container.
Assemblies of this type posses certain disadvantages and drawbacks. For example, since the lower edge of the skirt is exposed, it presents an accessible gripping edge for forcing cap removal. The cap is also susceptible to release by prying with an instrument which is easily engaged under the exposed lower edge of the skirt. The skirt bead and container bead extend the full circumference of the cap and container. Accordingly, the cap and container beads must be matched within narrow tolerance limits to function properly and it has been found that these tolerances are difficult to hold in mass produced assemblies. If the fit is too tight, cap removal is extremely difficult, even for adults, particularly elderly persons. On the other hand, a loose fit permits easy removal by the customary twist and pull techniques employed by young children.
Other safety closures which are snap cap arrangements are shown in the Grimm patent, No. 3,393,816, issued July 23, 1968, the U.S. Patent to Horvath, No. 3,812,989, issued May 28, 1974, the U.S. Patent to Berghahn, No. 3,757,979, issued Sep. 11, 1973, and the U.S. Patent to O'Donnell, No. 3,170,585, issued Feb. 23, 1965. These assemblies basically comprise a cap made of resilient material, such as plastic, having a locking rib which normally engages under a bead on the container neck. In some instances the cap has a discrete locking tab which registers with a gap in the bead on the container in the removal position for the cap. In each case visible, exposed indicia means are provided for registering the locking tab with the gap in the bead on the container neck. It has been found that these assemblies are likewise difficult to remove in some instances, even by adults, and furthermore, the alignment of the indicia means can be deciphered in some cases even by children.
With the foregoing in mind, the present invention provides a truly tamperproof container-closure assembly which is virtually impossible for young children to open and which nevertheless is relatively easily manipulatable by adults to position for opening when it is desired to gain access to the contents of the container. To this end the closure cap, which may be made of a resilient plastic material, is provided with a series of primary locking lugs on the interior side wall of the skirt and also a series of auxiliary lugs of a shallower radial depth than the primary lugs, which in the preferred embodiment, extend for a predetermined circumferential distance on either side of the primary lugs. The container neck is provided with a complementary bead interrupted at circumferentially spaced locations to define gaps of a slightly greater arc than the primary locking lugs on the cap so that the lugs may pass through the gaps in the release position. The circumferential spacing of the primary lugs and gaps are such that they register in only one position. By this arrangement, even when the primary lugs are in registry, the auxiliary lugs, which engage under the bead on the container, present a predetermined relatively small resistance to removal of the cap so that even if a young child were to align the primary lugs with the gaps by design or accidentally, the cap could not be easily removed if it were pulled in an axial direction. Cap removal is affected by engaging a thumb tab on the exterior of the cap side wall and pivoting the cap relative to the container. The lower edge of the skirt closely overlies a radial shoulder on the container neck to prevent removal by a prying action.
The assembly further includes a safety tear band connected to the lower edge of the skirt of the cap by fracturable means which tear band has a continuous circumferentially extending rib engaging under a locking band below the bead on the container neck. The band is interrupted to define an indicia slot or space for aligning the thumb tab to position the primary locking lugs in registry with the gaps for removal of the cap. The tear band normally overlies the gap and thus one element of the alignment indicia means is covered or not exposed prior to removal of the tear band. The lower edge of the tear band closely overlies a radial abutment surface on the container neck to prevent prying of the closure by use of an instrument. Thus, the present assembly is truly tamperproof and child resistant. The assembly also includes other features including sealing means for preserving the contents against deterioration.
The container and closure of the present invention lend themselves to mass production techniques and the cap and container are designed to be assembled by automatic equipment. Thus, the assembly is truly economical. Further, the tolerance to provide a truly child resistant assembly which is comparatively easy for adults to understand and operate are not as critical as in prior assemblies discussed above.